Cytotoxic leukocytes (NK, T lymphocytes, monocytes-macrophages) are potent effectors in the host defense against tumors. In vitro expansion and enhancement of the tumoricidal potential of autologous effector cells and their subsequent reinfusion into the host are currently being used in local or systemic adoptive immunotherapy (Rosenberg et al.: Progress report on the treatment of 157 patients with advanced cancer using LAK cells and IL2 or IL3 alone. N. Engl. J. Med. 316: 889, 1990; Rosenberg et al.: Use of tumor infiltrating lymphocytes and IL2 in the immunotherapy of patients with metastatic melanoma. N. Engl. J. Med. 319: 1676, 1990; Lacerna et al.: Adoptive cancer immunotherapy utilizing lymphokine activated killer cells and IFN-.gamma. activated killer lymphocytes. Pharm. Ther. 38: 453, 1988).
Macrophages play a central role in the antitumoral response and can be activated against neoplastic cells by immunopotentiators (Adams D. and Hamilton T.: Activation of macrophages for tumor cell kill: effector mechanism and regulation. In Heppner & Fulton (eds), Macrophages and cancer. CRC Press, 1988, p. 27; Fidler I.: Macrophages and metastases. A biological approach to cancer therapy. Cancer Res. 45: 4714, 1985).
In murine models, it has been demonstrated that activated macrophages given locally in the tumor inhibited tumor growth and decreased metastatic development (Bartholeyns et al.: Immunotherapy of cancer: experimental approach with activated macrophages proliferating in culture. Cancer Detect. & Prev. 12: 413, 1988; Chokri et al.: Antitumoral effect of LPS, TNF, IFN and activated macrophages: synergism and tissue distribution. Anticancer Res. 9: 1185, 1989). Human monocytes isolated from blood could be differentiated in vitro into macrophages by a 7 day culture in hydrophobic bags (Chokri et al.: Antitumoral effects of LPS, TNF, IFN, and activated macrophages: synergism and tissue distribution. Anticancer Res. 9: 1185, 1989). After incubation in the presence of IFN-.gamma., these macrophages became activated and tumoricidal, (Macrophages activated killer=MAK) for a number of human tumors in vitro or for tumors engrafted in nude mice (Andreesen et al.: Surface phenotype analysis of human monocytes to macrophages differentiation. J. Leuk. Biol. 47; 490, 1990; Dumont et al.: Control of the antitumoral activity of human macrophages produced in large amount in view of adoptive transfer. Eur. J. Cancer 24: 1691, 1988).
Adoptive transfer of MAK has undergone phase I clinical trials by different investigators in Strasbourg, Freiburg and Paris for patients with metastatic cancer infused systematically or intraperitoneally with 10.sup.8 to 2.times.10.sup.9 autologous MAK (Andreesen et al.: Adoptive transfer of tumor cytotoxic macrophages generated in vitro from circulating monocytes: a new approach to cancer immunotherapy. Cancer Res. 50: 7450, 1990; Bartholeyns et al. Adoptive immunotherapy of solid tumors with activated macrophages: experimental and clinical results. Anticancer Res. 11: 1201, 1991; Lopez et al.: One step separation by elutriation of monocytes from leukapheresis products of cancer patients for production of IFN-.gamma. activated macrophages in view of adoptive immunotherapy. J. Immunotherapy, 11: 209, 1992; Faradji et al.: Phase I trial of IV infusion of ex-vivo activated blood derived macrophages in patient with non small cell lung cancer: toxicity and immunomodulatory effects. Cancer Immunol. Immunother. 33: 319, 1991).
The clinical tolerance was excellent with minor side effects such as low grade fever and chills. The maximal tolerated dose could not be attained due to the limited number of MAK generated from one cytapheresis.
The recovery of larger quantities of MAK is therefore a need for optimal antitumoral efficacy in clinical trials and in therapy.
The macrophages prepared thus far in the conventional culture medium are obtained in a yield which is less than about 40%.
However, the need for macrophages presenting a higher cytotoxic activity is present in order to increase the efficacy in vivo and, subsequently, to delay the next macrophage administration.